Absorbent layer for use in hospital supplies

ABSTRACT

An absorbent fleece for use in hospital supplies, comprises a fiber blend of about 80-95% viscose and 10% polyester formed into a dry laid, nonwoven web, wherein the web consists of multiple, carded and cross-lapped layers that are consolidated using a needle-punch process, whereby the fleece has a water absorbtion of at least about 1,000 wt % and an absorbing speed of at least about 20 mm after 10 seconds.

[0001] This application is a continuation-in-part of provisional application 60/288,036, filed May 2, 2001, and incorporated by reference herein as if set forth in full. The present invention relates to absorbent products for use in hospital supplies such as mattress pads and medical dressings. A synthetic, non-woven fleece, initially designed for use in janitorial services, is highly flexible, low linting, solvent resistant, breathable, and sterile. It also has good physical integrity and ease of use. Further, it has a range of absorbency that is higher than materials in current use, without being so great as to encourage excessive fluid loss. These materials are also cost-effective.

FIELD OF THE INVENTION BACKGROUND OF THE INVENTION

[0002] Many different materials and structures have been suggested for wound dressings, but as a practical matter, the dressings that are most widely used in hospitals have remained substantially unchanged for at least about thirty years. Many of the improved dressings are elaborate and expensive to produce, and some rely on materials that are difficult to use.

[0003] For example, U.S. Pat. No. 3,422,817 issued to Mishkin et al., Jan. 21, 1969 relates to a tracheotomy bandage that uses a resilient frame instead of adhesive to position the bandage. The patent is non-specific with respect to the absorbent materials that might be used.

[0004] U.S. Pat. No. 5,939,339 issued to Delmore et al., Aug. 17, 1999 relates to a compression bandage that can utilize any known material as the absorbent layer, including foam, woven or nonwoven material including but not limited to rayon, polyester, polyurethane, polyolefin, cellulose, cellulose derivatives, cotton, orlon, nylon, or hydrogel polymeric materials as well as a nonwoven matrix plus a highly hydrophilic fluid absorbing material such as modified starches and high molecular weight acrylic polymers such as acrylonitrile fibers treated with alkali metal hydrides. This patent discloses that extremely absorbent materials are preferred.

[0005] U.S. Pat. No. 3,858,585, issued to Chatterjee, January, 1975, relates to the use of absorbent fibers make of alkali metal salts of carboxyalkyl cellulose. These highly absorbant materials are swellable in water. This application relates to a cross-linking treatment for the fibers that reduces their solubility in water and the consequent tendency to yield a granular or gel-like mass.

[0006] U.S. Pat. No. 5,941,840 issued Aug. 24, 1999 to Court, et al., relates to a multilayered wound dressing that includes a wound contact layer, an absorbent layer that can include viscose, polyester, and bi-component fiber structure with a gel-forming polymer that coats one side of the absorbent layer, and a hydrophobic layer. This structure is designed to maximize the liquid-absorbing properties of the gel-forming polymer.

[0007] U.S. Pat. No. 6,075,177, issued to Bahia, et al., Jun. 13, 2000, relates to non-crosslinked carboxymethylcellulose filaments capable of absorbing at least 15 times their weight of saline solution, which retain enough fibrous character when wet to be removable as a coherent dressing from a wound, and discloses blending the carboxymethylcellulose fibers with up to 50% by weight of other fibers to strengthen the dressing.

[0008] U.S. Pat. No. 5,830,496, issued to Freeman, Nov. 3, 1998 relates to a quilted multilayer laminate structure that can include a swellable material and yet remain dimensionally stable.

[0009] U.S. Pat. No. 6,348,423, issued to Griffiths, et al., February 2002, relates to a wound dressing that includes an odor absorbent layer. The application discloses the use of any known absorbent fibers, and also discloses that highly absorbent fibers (at least 25 g/g) are preferred.

[0010] U.S. Pat. No. 6,077,526, issued to Scully, et al., Jun. 20, 2000, relates to a wound dressing that uses a layer of graduated density felt to protect the wound from an absorbent layer make of highly absorbent fibers, to reduce the aggressiveness of absorption.

[0011] U.S. Pat. No. 4,667,665, issued to Blanco et al., May 26, 1987 relates to a burn dressing that comprises a non-adherent polyethylene film exterior covering and an inner absorbent layer composed of five percent cellulose strata and a strata of non-woven polyester and rayon material. This dressing uses two separate fabrics for the absorbent layer, which must be purchased separately and then combined and formed together, thus adding manufacturing steps that are not needed if the present invention is used.

[0012] U.S. Pat. No. 4,203,435 issued to Krull et al. May 20, 1980 relates to a multilayered dressing comprising at least 5 layers: two exterior layers of nonwoven fleece with low wound adherence, two absorbent layers containing cellulose fibers and synthetic fibers, and a distribution layer, such as tissue paper, between the absorbent layers. One of the disclosed absorbent layers is said to be 80% viscose and 20% polyester. Once the several layers are assembled, the entire dressing must be treated to reduce the presence of lint.

SUMMARY OF THE INVENTION

[0013] The present invention relates to the use of a material from an unexpected source as an absorbent in hospital dressings and supplies. More specifically, it relates to the use of a synthetic, nonwoven fleece as an absorbent layer is hospital dressings, wherein, the fleece is an 80-90% viscose, 10-20% polyester blend, having a fiber density of about 3-5 g/cm² and is available in various thicknesses and weights from Konus Konex d.o.o. Pe Netex, Konjice, Slovenia.

[0014] In a preferred embodiment, the fleece is about 90% viscose (dtex 1,7—3.3/40-60 mm), and 10% polyester (dtex 1,7—3.3/40-60 mm), having an area weight of 180-200 g/m² and a thickness of about 2.0-2.2 mm. The fleece has a water absorbtion of greater than 1200 wt % as measured by DIN 53923, and a water absorbing speed of greater than 20 mm in 10 seconds, greater than 30 mm in 30 seconds, greater than 40 mm in 60 seconds, and greater than 55 mm in 300 seconds as measured by DIN 53924. The fabric further has a tensile strength (L) if >100 N/5 cm, tensile strength (T) >150 N/5 cm, elongation (L) <70%, elongation (T) <60%, all measured according to DIN 53857. Its schopper abrasion resistance is max. 15 g/m²according to DIN 53863.

[0015] In another preferred embodiment, the fleece is about 90% viscose (dtex 1,7—3.3/40-60 mm), and 10% polyester (dtex 1.7—3.3/40-60 mm) bicomponent fiber where the bicomponent fibers have a softening point of between 220-120° C., having an area weight of about 180-200 g/m² and a thickness of about 1.8-2.0 mm. The fleece has a water absorbtion of greater than 1000% as measured by DIN 53923, and a water absorbing speed of greater than 25 mm in 10 seconds,, >35 mm in 30 seconds, >45 mm in 60s, and >70 mm in 300s, all as measured by DIN 53924. The fabric further has a tensile strength (L) of >150 N/5 cm, tensile strength (T) >150 N/5 cm, elongation (L) <70%, elongation (T) <60%, all measured according to DIN 53857. Its schopper abrasion resistance is max. 20 g/m² according to DIN 53863.

[0016] In each case, the fabric is highly flexible, low linting, solvent resistent, breathable and sterile, as well as being cost effective. The fabric has an absorbance range on the order of 10-15 grams per gram fabric that is greater than commonly used materials, but not so great as to encourage excess fluid loss from a wound.

[0017] An advantage of the present invention is that the material is easy to use, and that it requires a minimum of post-treatment during final product assembly to reduce linting. Another advantage of the present invention is that it is more absorbent than the materials in common use, without causing excessive fluid loss or suffering from loss of physical integrity, or requiring the addition of further materials. Yet another advantage is that the invention is very cost effective.

[0018] Embodiments of the present invention include the use of the presently described absorbent layer in mattress coverings and bed protectors, in burn dressings and rope dressings, gauze dressings, abdominal pads, rope dressings, laparotomy sponges, endoscopic bullet sponges, tracheotomy dressings and gastrointestinal dressings.

[0019] A specific embodiment of this invention would be the use of the absorbent layer in mattress coverings, particularly air mattress coverings for burn victims. Such burns frequently have a large amount of exudate, and in addition are often covered with copious amounts medicinal gel. It is desirable to have an absorbent protective cover for surfaces that will contact the patient, but such covers should not be too aggressively absorbent. In some cases, it is sometimes preferable to also include a covering that allows fluids to penetrate and yet remains dry to the touch. Such covering layers are known and available, for example, under the Goretex and Telfa trademarks, and are available from a number of sources, including KCI, San Antonio, Tex. In other cases, the additional covering layer may not be preferred. For example, in a particularly preferred embodiment, a bed specifically designed for burn patients has moveable arm supports clamped to the bed frame. The bed also has significant electronic components that can be damaged by fluids. The paddle-like supports are concave, and preferably have a disposable absorbent contoured cover including the present invention for catching exudate and medicinal gels from the patient's arms.

[0020] In another embodiment, the absorbent layer is either constructed so it has a side that is not permeable to water, or is adhered to a material that is not permeable to water, such as a film, and may be covered with a water-permeable layer, to make a bed protector. Again, the product may include a skin contact layer that is permeable, dry-to-the-touch, and/or nonadherent to wounds, as desired for particular applications.

[0021] In another embodiment, the absorbent layer can be used in a rope roll dressing, such as a tracheotomy dressing or a sacral decubitus dressing, used for packing heel ulcers for diabetic patients. The rope roll dressing can be made from narrow strips of the present invention. In addition, the web of the present invention can be made to have a greater thickness, but the same fiber density, to produce a dressing with a larger cross-section. Where a degree of wound debridement is considered desirable, the rope roll dressing may be made of the present invention only, or covered with an adherent gauze. Where a non-adherent dressing is desired a non-adherent gauze or covering layer can be added.

[0022] In yet another embodiment, a burn dressing may comprise a non-adherent film or a gauze exterior covering and an inner absorbent layer of the present invention.

[0023] In a further embodiment, a tube dressing, comprising a small square of fleece with a cut from the perimeter to about the center can be made using the present invention. For example a 5×5 cm square of fleece can be cut to fit a gastrointestinal or tracheotomy tube.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The absorbent layer of the present invention is a fleece made of a blend of about 80-95% viscose and about 20-5% polyester. In a preferred embodiment, the blend is about 90% viscose and 10% polyester; in another preferred embodiment, the blend is about 90% viscose and 10% bicomponent fiber blend that can be polyester or another bicomponent blend such as polyethylene/ethylvinyl acetate having a softening point between 110 and 120° C. Examples of suitable fleeces are available as UNI MED 200 and UNI MED C 200, from Konus Konex, Slovenia.

[0025] A dry laid, nonwoven web is produced using principles and machinery known to the textile or pulp fiber handling industry. First, the fiber blend is selected and loose fibers are mixed so that they are fairly evenly distributed in a large container. Then the fibers are carded, that is, passed through a series of steel rollers covered with saw teeth so that the fibers are “combed” and generally aligned with one another. The carded fibers are condensed by passing the fibers through a pair of smooth rollers having a fixed gap, or nip. The resulting fiber layer is light, diffuse, and too fragile to be used as a fabric.

[0026] Several carded fiber layers are arranged in combination to make multiple fiber layers, or plies, that are laid on top of one another in a Cross-Lapping process. The number of fiber layers, together with the needlepunching and other finishing steps, determines the thickness of the final product. In a preferred example, multiple layers are used, the Cross-Lapped layers are applied at a nominal 90° angle to the machine direction of the base web and the resulting angles at which the crosslapped layers are applied vary with the relative rates of the web advance and Cross-Lap machine speed. The Cross-Lapping process assures that the orientation of the fibers in the different fiber layers can be varied, so that parallel and cross-laid layers can be combined. The Cross-Lapping process improves final product strength, absorbancy and speed of absorbance.

[0027] The various fiber layers of the web are then consolidated. In a preferred embodiment, the fibers are mechanically bonded in a needle-punch process. Barbed needles arranged on a plate or cylinder are pressed into the web from both sides, penetrate into the multilayered web and then recede, leaving the fibers entangled, and consolidating the web somewhat. This process improves the fabric strength, appearance and abrasion resistance and absorbance. The degree of fibrous entanglement is manipulated by varying the needle configuration, length, barb shape, and density of needle punches, which depends in part upon the web advance rate. In the preferred embodiments, the needle configuration is random, The needle type is G.B. 15×18×38×3 M222 G3017, and the number of needle punches per square meter from the top is 170-190, while the number of needle punches per square meter from the bottom is 88. The resulting web can be used directly for an absorbent layer in medical products, or may 5 be subjected to further finishing treatments.

[0028] For example, the fleece may be point-bonded. In a preferred embodiment, the polyester portion of a preferred blend may be formed from a bicomponent binder fiber blend having a softening point of between 110 and 120° C. These fibers soften and may melt under appropriate treatment, such as when the web is passed through twin rollers and exposed to steam heat in the target temperature range of 110 and 120° C. in a calendering process. The result is a fleece that is slightly thinner than the web described immediately above, and has a lower total water absorbance, but a higher water absorbing speed.

[0029] The (optionally) bonded web may be used directly in a product, or may be further processed in a variety of finishing steps. Mechanical finishing steps include calendaring, brushing, embossing, laminating, creping and crushing.

[0030] Calendaring is a process where a web is passed through a series of heated or cold rollers. Different types and arrangements may be used for different effects, such as softening, imparting gloss, surface texture or affecting the hand (density or fullness to the touch) of a fabric. A calendaring process can be used bond the fabric, as described above, or add a coating. For example, one or both sides of the web may be treated with an acrylic or latex coating. This coating can, for example, serve as a moisture-retardant surface. The web can also be printed or dyed, or have an antimicrobial finish applied. Another layer of a different kind of material can added, such as a waterproof film. This is called lamination when the film is passed with the web between rollers that typically are heated and pressurized so that the film bonds to the web.

[0031] Embossing is a process where the web is passed through the nip of pressurized or possibly heated rollers, one or both of which may have a patterned surface, in order to impart a desired texture to the surface of the web. Creping can be considered a variation on embossing, that is intended to change the elongation and flexibility of the web by enlarging the web surface area. Crushing is a similar process that introduces crimp, stretchability and drapeability as well as softness to the web. Brushing is a process where the web is passed under one or more rotating brushes to give special surface effects. Typically, the surface fibers are raised to yield a soft or fur-like hand to the web. Over-brushing can result in increased linting, and is therefore preferred only if it is controlled.

[0032] Any of the mechanical finishing processes are easily compatible with medical end-uses, so long as they do not substantially add to lint formation or leachability of the end product.

[0033] Chemical finishes may also be applied to nonwoven webs. These include bleaching, dyeing, printing, sizing, or the addition of finishes to impart special traits such as antimicrobial or fire-retardent properties. Bleaching and dyeing, if performed, are preferably handled at the fiber stage. For medical applications, it is preferable to begin with virgin fibers and avoid the addition of any chemicals that might contact or leach into a wound, and so chemical finishes for webs that are intended as absorbent layers that may contact a wound are preferably those approved for use in wound contact applications.

[0034] Further, the various additives may be combined with the nonwoven web during manufacture, or applied to the finished fleece before or after its incorporation into a hospital product. Examples include but are not limited to antimicrobial gels, powders or liquids, pain relievers, odor absorbers and wound healing promoters. Specific examples include calcium alginate (to reduce bleeding time) Banzalkonium chloride and silver compounds (reduce infection), activated charcoal (reduces odor), lidocane hydrochloride (relieves pain), collagen alginate and Becalpermin (promote wound healing). 

What is claimed is:
 1. An absorbent fleece for use in hospital supplies, comprising a fiber blend of about 80-95% viscose and 10% polyester formed into a dry laid, nonwoven web, wherein the web consists of multiple, carded and cross-lapped layers that are consolidated using a needle-punch process, whereby the fleece has a water absorbtion of at least about 1,000 wt % and an absorbing speed of at least about 20 mm after 10 seconds.
 2. The absorbent fleece of claim 1, wherein the fiber blend is about 90% viscose and 10% polyester.
 3. The absorbent fleece of claim 2, wherein the polyester is a bicomponent fiber blend having a softening point between 110 and 120° C. 